81787719 has 16 divisors (see below), whose sum is σ = 118143200. Its totient is φ = 50326848.

The previous prime is 81787711. The next prime is 81787721. The reversal of 81787719 is 91778718.

It is not a de Polignac number, because 81787719 - 2³ = 81787711 is a prime.

It is a super-2 number, since 2×81787719² = 13378461958445922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81787711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 387 + ... + 12795.

It is an arithmetic number, because the mean of its divisors is an integer number (7383950).

Almost surely, 2^81787719 is an apocalyptic number.

81787719 is a deficient number, since it is larger than the sum of its proper divisors (36355481).

81787719 is a wasteful number, since it uses less digits than its factorization.

81787719 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12451 (or 12425 counting only the distinct ones).

The product of its digits is 197568, while the sum is 48.

The square root of 81787719 is about 9043.6562849325. The cubic root of 81787719 is about 434.0729258697.

Subtracting 81787719 from its reverse (91778718), we obtain a palindrome (9990999).

The spelling of 81787719 in words is "eighty-one million, seven hundred eighty-seven thousand, seven hundred nineteen".